The present invention relates to annular type blowout preventers and similar equipment used to control pressures while drilling a well, and more particularly to packing element elements and inserts used in such equipment. U.S. Pat. No. 2,609,836 to Knox and Canadian Patent No. 1,178,196 to Huey, Wai J. describes annular type blowout preventer packing units which incorporate metal inserts spaced about the packing element central axis, and embedded by a rubber body. Upon inward constriction of the unit about a well drill pipe, or upon itself, the rubber squeezed radially inwardly with resistance imposed by the inserts to which the rubber is anchored. Well pressure exerted upwardly upon the stretched or extended rubber also tends to displace it upwardly, so that the material, is subjected to strain both radially and vertically. This causes fatigue and weakening of the material, particularly after repeated closure of the preventer unit, so that each unit is normally rated as to its capability to safely sustain or withstand a certain number of closures, but the problem of extreme stretching of the rubber has limited the success of such efforts.
It is a major objective of the present invention to provide an improved blowout preventer unit characterized in that the capability of non-metallic composite inserts to effectively anchor the flexible non-metallic composite packing element under extreme well pressure is substantially enhanced, with the result that fracturing of the packing element is substantially reduced, and with the result that the life of the preventer unit is materially enhanced.
It is therefore an object of the present invention to provide non-metallic composite inserts for use in a packing element wherein the leading and trailing edges of the non-metallic composite insert exhibit a relatively large, and arcuate surface area so as to reduce the stress and strains developed at the bond line between the inserts and the flexible non-metallic composite body in the packing element.
It is an object of the present invention to provide such a non-metallic composite insert that eliminates the risk of generating sparks when in contact with drill string when tripping or stripping in and out of the well bore. Eliminating sparks is very important, as these sparks are known causes of fires and explosions.
It is a further object of the present invention to provide such a non-metallic composite insert that eliminates metal use in conventional inserts so that the over all weight of the blowout preventer is substantially reduced.
It is a still further object to provide a non-metallic composite insert having a dumbbell shaped cross-section, somewhat like an I-beam in construction, to provide efficient load bearing capabilities through the geometry of the insert.
These and other objects and advantages of the invention, as well as the details of illustrative embodiments, will be more fully understood from the following description and drawings.